1. A case of aleukemic myelosis with leuko-erythroblastic anemia is presented, in which the development of extramedullary hematopoiesis in liver and spleen, and fibrosis of marrow was studied by multiple punch biopsies and eventual autopsy.
2. This case offers further support to the theory that many cases of marrow fibrosis are fundamentally leukemic in nature belonging to the group of atypical granulocytic leukemias (aleukemic myelosis).
3. The extramedullary hematopoiesis in this case was interpreted as being of leukemic nature rather than a compensatory metaplasia.
4. Since there are other definite causes of marrow fibrosis and since no adequate etiology has been found to explain some cases, it is suggested that marrow fibrosis be classified as (a) primary idiopathic or (b) marrow fibrosis secondary to aleukemic myelosis, neoplasm, chemical toxins etc.